Development of Injectable Fiducial Markers for Image Guided Radiotherapy with Dual MRI and CT Visibility

Abstract

Radiation therapy or radiotherapy (RT) is a powerful treatment where precision and accuracy is crucial. Image Guided Radiotherapy (IGRT) facilitates more accurate position verification, correcting for anatomic changes related to internal organ movement. IGRT thereby helps reduce toxicity of radiotherapy and increases relapse-free survival. An inter-correlation point with a fixed position and volume (a marker) can be applied to indicate the point of treatment clearly in both imaging modalities and to localize and track tumors in real time. In this study, we present the development of a marker based on lactose octaacetate:octapropionate 1:1 containing 3 mM PLA-DTPA(Gd), 40% triglyceride, 5% propylene carbonate and 10% XSAIB (sucrose based CT-contrast agent). The injectable marker had high CT contrast (>1000 HU) and displayed clearly visible, stable T1 contrast enhancement (T1˜0.900 ms) in the rim over at least 3 weeks with clinically observable resolution.

Description

INTRODUCTION[0001]Radiation therapy or radiotherapy (RT) is an important therapy form used in combination with surgery and chemotherapy for the treatment of cancer [1]. Radiotherapy relies on the use of ionizing radiation, and is therefore very dependent on precision and accuracy.[0002]Therefore, increasing emphasis is being laid on optimizing radiotherapy volume while facilitating tumor targeted delivery of high radiotherapy doses, resulting in a more efficient treatment with reduced risk of radiation damage to adjacent normal tissues [2]. Image Guided Radiotherapy (IGRT). IGRT facilitates more accurate position verification during the course of fractionated radiotherapy in order to correct for change in tumor position related to internal organ movement caused by respiration, peristalsis and rectal / bladder filling [3]. Thereby IGRT helps reduce toxicity of radiation treatment while leading to a higher fraction of relapse-free survival [4].[0003]The most frequently used imaging-tech...

AI Technical Summary

Benefits of technology

The patent text discusses the use of image guided radiotherapy (IGRT) to optimize radiotherapy treatment and reduce the risk of radiation damage to adjacent normal tissues. The text also describes a new formulation of a contrast agent called 3 mM PLA-DTPA(Gd) that is used to verify tumor position during treatment. The results of the clinical trial using this contrast agent are promising, with the agent showing stability and enhancement of contrast in a clinical setting. Overall, the technical effects of the patent text are increasing emphasis on optimizing treatment efficacy while reducing toxicity and the use of innovative techniques to improve the accuracy and precision of radiotherapy.

Problems solved by technology

However, CT-based target delineation of soft tissue tumors tends to only improve the precision and not the accuracy of tumor delineation for radiotherapy treatment.

While SAIB-based markers are readily visible in the CT modality due to the high content of heavy atoms (Au or I), the markers result in a hypointense signal in T1-weighted MRI, often difficult to visualize in tumor tissue [16].

The systems described in literature mainly consist of hydrophilic polysaccharides such as chitosan and hyaluronan functionalized with Gd chelators [19, 20] displaying high T1 contrast and retention in tumors lasting several days, however these hydrophilic systems are often not injectable in sufficiently high concentrations, therefore nanoparticle formulations are constructed, and clearance of such particles is relatively fast (within days) from the tumor area, requiring repeated administration.

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